(a) They're making millions, you deserve a cut of that.
(b) If making money makes you more likely to be around in 10 years, that's attractive to businesses. Nobody knows when your donations might suddenly dry up.
I honestly believe this project can cover $175 per month eventually.
Of course there is the countless hours which went and which can possibly go into this, but to cover the hosting is still meaningful.
Let's say 1 year from now your day job gets toxic and you have to work 18 hours a day just to pay your rent and expenses. Are you still going to maintain this?
What if the economy goes to shit and you have trouble scraping that $175/month? How long are you going to pay $175/month for something that isn't making money?
What if, instead, this became a part-time job of yours?
If I was a commercial user of your product, some assurance that your random personal situations aren't going to affect the product stability for a long time would be a good thing.